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Ōita-shi, Japan

Sugiyama Y.,Kitabesso 23 3 | Kurita H.,Board of Education | Matsui T.,Takasakiyama Natural Zoo | Shimomura T.,Takasakiyama Natural Zoo

In a wild-living, artificially provisioned population of Japanese macaques at Takasakiyama in southern Japan, nine sets of twins were recorded from 12,392 known deliveries over a 56-year study period. Recorded twinning frequency was 0.073%. During the first 28-year period, artificial food was given until macaques were satiated and population size increased rapidly. In the second 28-year period, provisioned food was restricted to about half of the former period's calorific content. Seven sets of twins were born in the first period and two sets in the second. Twining frequency in the two periods was 0.137 and 0.027%, respectively. In comparing studies of other Catarrhine primate samples, we hypothesize that twinning frequency is influenced by living conditions, and we suggest that living conditions should be carefully evaluated in studies of twinning frequency. © 2010 Japan Monkey Centre and Springer. Source

Sugiyama Y.,Kyoto University | Kurita H.,Board of Education | Matsui T.,Takasakiyama Natural Zoo | Kimoto S.,Takasakiyama Natural Zoo | Egawa J.,Takasakiyama Natural Zoo

From the late 1960s to the early 1970s, many congenitally malformed infants were born into provisioned Japanese macaque troops. Although the exact cause of this problem was not determined, the occurrence of malformations decreased thereafter. We examined possible factors such as total population size, number of adult females, birth rate, and volume of provisioned food. Agrichemicals attached to provisioned food are suspected as the main cause, as other factors were found to have no influence. Many more malformations were seen in males compared with females, in feet compared with hands, and in the fourth compared with other digits. We confirmed that the frequency of congenital malformation was high during the 1960s through to the mid-1970s when increased levels of provisioned food were given and that the incidence of congenital malformations was also elevated among wild macaques during this time. © 2014 Japan Monkey Centre and Springer Japan. Source

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